How to copy compositing nodes from on file to another?
File -> Append -> select your file -> NodeTree -> choose the node group you want.

The same method works for all kinds of data (shaders, meshes, etc.).

EDIT: I just reread your question and realized that for whatever reason you don't want to group the nodes. I think my solution only works for a group of nodes. I don't know if there's a way to do it without grouping them.